DEVELOPMENT OF COMPACT VARIABLE-VOLTAGE, BI-DIRECTIONAL 100KW DC-DC

CONVERTER

Leonid Fursin1, Maurice Weiner1

Jason Lai2, Wensong Yu2, Junhong Zhang2, Hao Qian2

Kuang Sheng3, Jian H. Zhao3, Terence Burke4, and Ghassan Khalil4

1United Silicon Carbide, Inc., New Brunswick Technology Center, Building A, New Brunswick, NJ 08901, USA

2FEEC, ECE Department, Virginia Tech, Blacksburg, VA24060, USA3SiCLAB, ECE Dept., Rutgers University, 94 Brett Road, Piscataway, NJ 08854, USA

4 U.S. Army TARDEC, Warren, MI 48397-5000, USAfor

AECV-2007

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1. REPORT DATE 11 JUN 2007

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4. TITLE AND SUBTITLE Development of Compact Variable-Voltage, Bi-Directional 100KWDC-DC Converter

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) Leonid Fursin; Maurice Weiner; Jason Lai; Wensong Yu; JunhongZhang; Hao Qian; Kuang Sheng; Jian H. Zhang; Terence Burke;Ghassan Khalil

5d. PROJECT NUMBER

5e. TASK NUMBER

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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) US Army RDECOM-TARDEC 6501 E 11 Mile Rd Warren, MI 48397-5000

8. PERFORMING ORGANIZATION REPORT NUMBER 17101

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13. SUPPLEMENTARY NOTES Presented at the 7th AECV Conference, June 11-13, 2007, Stockholm, Sweden, The original documentcontains color images.

14. ABSTRACT

15. SUBJECT TERMS

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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18

OutlineOutlineProject goalsPower Stage DesignDSP controller, interface circuit and gate driver implementationPower stage layout and packagingConverter testing Summary and Conclusions

Project GoalsProject Goals

Bidirectional dc-dc converter targets: Input voltage range: 200 - 300 VDC (battery pack voltage) Output voltage range: 300 - 600 VDC Bidirectional power flow Continuous Power: 100 kW, Peak: 150kWPower density: 4 to 8 kW/literSpecific power density: 4 to 6 kW/kgTotal efficiency: ≥ 95%SVM frequency: ~20kHzCoolant Temperature: ≥ 90oC

InnovationsInnovationsA novel yet simple zero-voltage soft-switching scheme

without adding any extra switchmaking a 25KHz switching frequency possible

High-end digital signal processor controllerallow fast and smooth mode transition

An interleaving 3-phase designsubstantially reducing the ripple current and filter capacitor size

Nano-inductor designHigh permeability, high saturation flux density lead to small inductor size

SiC Schottky diode-Si IGBT power modules Minimized thermal resistanceRobust diodes, zero-recovery charge

POWER STAGE DESIGN

Proposed Soft-switching Bi-directional DC/DC Converter with Lossless SnubbersProposed Soft-switching Bi-directional DC/DC Converter with Lossless Snubbers

Load/Source

Ld1

Ld3

S1u S2u

S1d S2d

300 -800 VH

igh

freq

. cap

.

S3u

S3d

Ld2

200 -300 V

C

A special switching scheme that utilizes unused switches to perform soft switching: The basic idea is to have the unused switch turned on while the active switch is turned off.

This will allow current continuously flow in opposite direction, thus avoiding the discontinuous current and parasitic ringing. Now to reduce the turn-off loss, we can put the lossless snubber

across the device to slow down the rate of switching.

Overall hardware system structure: power stage, gate driver and DSP controller

Overall hardware system structure: power stage, gate driver and DSP controller

TMS2808

GATE DRIVER

Power Stage in Bidirectional Soft-switched DC/DC Converter

V-low

V-high

A0

A1

000

01

A0

Boost-I10Boost-V00

Buck-V01

Buck-I11Stopxx

ModeA2A1

I –inductor3

I –inductor2

I –inductor1

A2

SIGNALCONDITIONING

EP

WM

ADC G

PIO

SYSTEMCLOCK

INTERRUPT SYSTEM

DSP Controller

TMS2808

GATE DRIVER

Power Stage in Bidirectional Soft-switched DC/DC Converter

V-low

V-high

A0

A1

000

01

A0

Boost-I10Boost-V00

Buck-V01

Buck-I11Stopxx

ModeA2A1

I –inductor3

I –inductor2

I –inductor1

A2

SIGNALCONDITIONING

EP

WM

ADC G

PIO

SYSTEMCLOCK

INTERRUPT SYSTEM

DSP Controller

Summary of Testing Results of IGBT LossSummary of Testing Results of IGBT Loss

0

10

20

30

40

50

60

0 50 100 150 200 250 300 350

Current (A)

Turn

-off

ener

gy (m

J)

w/o capacitor

with 0.14μF

VDC=700V, Csnub= 0.14μF

×3 loss reductionAchieved without extra switches/inductors

Inductor DesignInductor Design

A superior core, FINEMET®, is usedHigh permeability, high flux density

Inductor Design Verification Inductor Design Verification

iC (100A/div)

iL (100A/div)vCE1 (100V/div)

vGE1 (10V/div)

t (5µs/div)

Saturation Point=456A

L=14.5μH, ISAT=456A, 20% design margin

Each inductor core:3.35kg, 0.47 liter

Liquid cooled heatsink designLiquid cooled heatsink design

Liquid-cooledθth<0.01°C/W

Physical Layout Dimensions of IGBTsPhysical Layout Dimensions of IGBTs

DSP controller, interface circuit and gate driver

implementation

Auxiliary Gate Drive Power SupplyAuxiliary Gate Drive Power Supply

0.50

19.65

7.0510.20

2.5415.24

1 2

5 6 7

4.10

1 2

5 6 7

MSV

H-241505

100mA

/–100mA

•C

TC

Pin no Function

1 +Vin

2 –Vin

5 –Vout

6 COM

7 +Vout

The gate driver power supply module provides isolated outputs of +15V and –5V at ≥90°C.

DSP TMS320F2808 function blocksDSP TMS320F2808 function blocks

Simulation results for the efficiency of boost mode and buck mode

Simulation results for the efficiency of boost mode and buck mode

0.90.910.920.930.940.950.960.970.98

400 450 500 550 600 650 700

Boost Mode

Output Voltage (V)

Effic

ienc

y

Vin = 200V

Vin = 300V

0.90.910.920.930.940.950.960.970.98

400 450 500 550 600 650 700

Boost Mode

Output Voltage (V)

Effic

ienc

y

Vin = 200V

Vin = 300V

Boost mode efficiency

0.90.910.920.930.940.950.960.970.98

400 450 500 550 600 650 700

Buck Mode

Input Voltage (V) Ef

ficie

ncy

Vo = 200V

Vo = 300V

0.90.910.920.930.940.950.960.970.98

400 450 500 550 600 650 700

Buck Mode

Input Voltage (V) Ef

ficie

ncy

Vo = 200V

Vo = 300V

Buck mode efficiency

Power stage layout and packaging

Converter moduleConverter moduleInductors

IGBT modulesGate driver board

Fiber-optical cables

• The DSP controller includes signal conditioning circuit and TMS320F2808 digital signal processor.

DSP controller with interface board

The IGBT driver circuit

• Provides electrical isolation by optocouplers, fiber optics, and by transformers• With overcurrent detection and pulse-by-pulse overcurrent protection function

The Power Stage Layout

• With minimized size of the inductors for 100kW output power• Zero-voltage switching on and zero-voltage switching off with capacitor• Compact bus capacitor size with Interleaving ripple cancellation

Converter testing with Coolant at 90oC

iL(100A/div)

iLall (100A/div)

vo (100V/div)

t(10µs/div)

iL(100A/div)

iLall (100A/div)

vo (100V/div)

t(10µs/div)

Measured Current Waveforms

Inductor current ripple is greatly reduced by interleaving three phases

Detailed Measured Waveforms in 100kW Load

• Switch is turned on under ZVS condition.

vGE (10V/div)

vCE (200V/div)

–iL (100A/div)

t(2µs/div) Turn-offTurn-on

Test condition : Vin=450V, Vout=280V, P=100KW

• Note that Inductor current negated.

Start-up Voltage and Current Waveforms at 108-kW Operation in Boost Mode

Start-up Voltage and Current Waveforms at 108-kW Operation in Boost Mode

Transient response of the converter under boost mode operation with a step load

change from no load to 80-kW

Transient response of the converter under boost mode operation with a step load

change from no load to 80-kW

200A

400V

ia (100A/div)

vo (200V/div)

io (100A/div)

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

Output Power (kW)

Effi

cien

cy (%

) Experimental ResultsAnalytical Results

• Maximum efficiency is around 97%

Test condition : Vin=450V, Vout=280V, buck mode

Experimental efficiencies in Buck Mode (450V input and 280V output)

50556065707580859095

100

0 10 20 30 40 50 60 70 80 90 100Output Power (kW)

Effic

ienc

y (%

)

Experimental ResultsAnalytical Results

Experimental efficiencies in Boost Mode(240V input and 360V output)

• Maximum efficiency is around 98%

SummarySummarySi-based soft-switching bidirectional DC-DC converter has been successfully demonstrated

Novel soft-switching circuit without extra switch/inductorDSP (TI-TMS320F2808), inductor, gate driver, optical fiber interface designed

Successfully tested at 90°C temperature for 30-kW continuous and 108-kW.Efficiency of 97-98% achieved in both buck and boost modesCompact size (less than 25 liters) demonstratedSiC/Si hybrid power modules being packaged for DC-DC converter operating at high coolant temperature >90oCSix phase interleaved design will reduce stress to inductors for robust long-term reliable DC-DC converter for FCS